Silent emergency alarm system for schools and the like

ABSTRACT

In a school each classroom (or other area) is instrumented with a hidden microphone and receiver tuned to a non-audible frequency. The receivers&#39;&#39; outputs are connected to a central display unit in the school&#39;&#39;s administrative office. Each instructor is provided with a small concealable transmitter which, when hand activated by the instructor upon the occurrence of any emergency, generates a non-audible signal at the receiver&#39;&#39;s tuned frequency.

Fletcher et a1. 31, 1973 [54] SILENT EMERGENCY ALARM SYSTEM 3,112,48611/1963 Adler 340/148 QR SCHQQLS AND THE LIKE 2,942,249 6/1960 Paull340/332 [76] Inventors: James C. Fletcher, Administrator of the NationalAeronautics and Space Administration with respect to an invention of;William S. Read, Glendale; Vnsel W. Roberta, La Cresecenta, both ofCalif.

[22] Filed: Aug. 6, 1971 [21] Appl. No.: 169,671

[52] US. Cl. 340/277, 340/279 [51] Int. Cl. G081) 7/06 [58] Field ofSearch 340/312, 148, 15, 340/277, 412, 279, 311, 287, 332; 35/1;

[56] References Cited UNITED STATES PATENTS Denny et aI. 340/277 PrimaryExaminer-lohn W. Caldwell Assistant Examiner--Glen R. Swann, IIIAttorney-Monte F. Mott,.lohn R. Manning et al.

[57] ABSTRACT In a school each classroom (or other area) is instrumentedwith a hidden microphone and receiver tuned to a non-audible frequency.The receivers outputs are connected to a central display unit in theschools administrative office. Each instructor is provided with a smallconcealable transmitter which, when hand activated by the instructorupon the occurrence of any emergency, generates a non-audible signal atthe receivers tuned frequency.

2 Claims, 7 Drawing Figures GNAL WIRE DISPLAY UNIT 24 ADMINISTRATIVEOFFICE I4 PATENTEDJUL 31 ms SHEET 2 OF 3 FIGZ 32A FMTR RCVR ESET SWBUZZER sw 68 58 {POWER SW. 57 nov 54 60m MIKE- FIG? WILLIAM s. READVASEL w. ROBERTS INVENTORS /Z Q WKWLW MIKE- SPEAKER FROM RELAY 45ATTORNEYS SILENT EMERGENCY ALARM SYSTEM FOR SCHOOLS AND THE LIKE ORIGINOF INVENTION The invention described herein was made in the performanceof work under a NASA contract and is subject to the provisions ofSection 305 of the National Aeronautics and Space Act of 1958, PublicLaw 85-568 (72 Stat. 435; 42 USC 2457).

BACKGROUND OF THE INVENTION 1. Field of the Invention The presentinvention relates to an emergency alert system and, more particularly,to a system for, and a method of, indicating the presence of anemergency in any chamber of a multichamber facility, such as a school orthe like.

2. Description of the Prior Art There are many multichamber facilitiesin which a particular condition, such as an emergency may arise in anyof the chambers. In such a facility it is often desirable to communicatethe existence of the emergency in the particular chamber to a centrallocation for summoning aid, speedily. In some cases it is desirable tocommunicate the existence of the emergency in a manner which is notnoticeable by persons in the chamber. For example, in some schoolsextreme disturbances have occurred in classrooms. Such disturbances haveresulted from an attack on the teacher or on a student by anotherstudent or by an unauthorized person, invading the classroom. Studentwalkouts have also precipitated the need for assistance. Coping withsuch occurrences is sometimes beyond the physical capability of theinstructor, particularly when the disruption is occasioned by unknownintruders.

It is desirable in such instances for the maintenance of order or toobtain police intervention, to make it possible for the instructor tosummon help in a discreet manner. It is apparent that this capabilitywould be beneficial to orderly school administration.

Similar situations may arise in different chambers or sections of aprison or like facility in which it is desirable to alert and requesthelp to cope with an emergency in any compartment of the facility insuch a manner that those in the compartment or room are not aware thataid is being requested. Although various emergency alarm systems are inexistence in various facilities none exhibits such capabilities.

OBJECTS AND SUMMARY OF THE INVENTION It is a primary object of thepresent invention to provide a new improved emergency alarm system for amultichamber facility to enable the indication of an emergency in any ofthe chambers.

Another object of the present invention is to provide a method ofindicating at a central location the existence of an emergency in anychamber of a multichamber facility and the particular chamber in whichthe emergency exists.

A further object of the present invention is to provide a new smallmanually activatable transmitter of nonaudible signals.

The invention will be described in connection with a school although itis equally applicable to other facilities in which similar requirementsexist. The aforementioned and other objects are achieved by concealingone or more sensors, hereafter also referred to as microphones, capableof sensing a non-audible signal in each of the classrooms or otherinstrumented areas, e.g., school cafeteria and gym. The sensor in eachroom is connected to a receiver, which is in turn connected to a centralunit at a central location. Each instructor is provided with a small andinconspicuous handoperated non-audible signal generator. The nonaudiblesignal will hereafter also be referred to as a supersonic signal. Whenan emergency arises in a room the instructor impulses the generator toproduce the supersonic signal which is picked up by the sensor in theroom. Its output activates the receiver, which in turn activates in adisplay unit at a central location a buzzer as well as illuminates anindicator, such as a lamp, indicating the particular room in which theemergency exists. The output of each receiver may also be used toactivate a two-way communication system to enable supervisory personnelat the central location to communicate audibly with the instructor inthe room in which the emergency exists.

The novel features of the invention are set forth with particularity inthe appended claims. The invention will best be understood from thefollowing description when read in conjunction with the accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a partial diagram of aschool instrumented with the present invention;

FIG. 2 is a general block diagram of the system of the presentinvention;

FIG. 3 is a schematic diagram of one embodiment of a receiverincorporated in the present invention;

FIG. 4 is a partial schematic and block diagram of a display unit shownin FIG. 1;

FIGS. 5 and 6 are diagrams useful in explaining a novel supersonicsignal generator; and

FIG. 7 is a partial block diagram of a two-way communication system,controlled in accordance with the teachings of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The implementation of theteachings of the present invention in a school may best be explained inconjunction with FIG. I. Therein numeral designates a classroom in aschool I2, which includes an administrative office 14. In the classroomII) a sensor or microphone 16, designed to pick-up acoustic energy isinstalled such as in ceiling 18. The microphone is connected to areceiver 20 by means of wires 21. The receiver in turn is connected bywires 22 to a display unit 24, located in the administrative office I4.The receiver, which is preferably located adjacent the microphone, is anarrowband receiver and amplifier, and is tuned to provide an activatingsignal only when an acoustic signal within the narrowband is sensed bythe microphone. In practice the receiver is tuned to a supersonicfrequency above the audio range, e.g., 40-45 kI-Iz.

When a signal of the tuned frequency is received, the receiver providesthe activating signal which, when received by the display unit, causesthe illumination of an indicator, e.g., a lamp, to indicate the room inwhich the supersonic signal was detected. The display unit includes onelamp for each area (such as the classroom) that is instrumented with amicrophone and a receiver,

and the designation of the ramp in the display unit corresponds to thelocation whereat a supersonic signal was detected. In a preferredembodiment, the display unit includes a buzzer which is activatedwhenever any of the receivers provides an activating signal. The buzzeris used to alert administrative personnel to view the display unit anddetermine the room in which the supersonic signal was detected.Preferably, the buzzer and the illuminated lamp remain activated untilthey are reset by an operator.

The instructor, designated in FIG. 1 by numeral 30, in each classroom orother instrumented area is provided with a hand-activatable transmitter32. The latter when activated by the instructor produces a supersonicsignal represented by line 26 which is picked up by the microphone 16.As will be pointed out hereafter, the transmitter operates frommechanical energy that is stored by manually compressing a spring. Whenthe spring is released by the instructor, a tuned bar of the transmitteris struck, and the bar vibrates at its resonant frequency. The latter isselected to correspond to the receivers tuned frequency.

In the transmitter, contemplated herein, the bar is undamped except forthe friction provided by its mounting arrangement. Thus the bar vibratesfor an appreciable period to insure proper signal detection by themicrophone. This is unlike prior art television remote control units inwhich bar vibration is damped so that each vibrating bar produces singlepulse supersonic (or subsonic) television activating signals. Thuswhereas in the prior art each transmitter activation produces a singlepulse of supersonic energy at the vibrator's resonant frequency, in thepresent transmitter each transmitter activation results in a ringingeffect of supersonic energy.

Attention is now directed to FIG. 2 which is a simple block diagram ofthe circuitry used in practicing the present invention. Therein it isassumed that the school includes A-N instrumented areas. Microphones16A-l6N and receivers 20A-20N are installed in the areas A-Nrespectively. In the particular diagrammed arrangement, the display unit24 is shown including relays 40A-40N which are enabled by the outputs ofreceivers 20A-20N respectively, to enable the supply of power from anappropriate source (not shown), to lamps L L respectively. The outputsof the relays 40A-40N are assumed to be connected to a buzzer 40 throughan OR gate 42 so that whenever any of the relays is activated or on, inaddition to enabling the illumination of the lamp with which it isassociated, it also activates the buzzer 40. The relay circuit isdesigned to hold the relay ON until it is reset. The circuit may includea reset button to reset the relay by switching it to OFF and therebydeactivate the illuminated lamp and the buzzer. As is appreciated, thesystem further includes transmitter 32A32N which are carried byinstructors in areas A-N, respectively.

It should be apparent that various known circuit design techniques maybe used in implementing the cireuitry of the present invention.Generally, the novelty of the invention is in. the combination ofcircuits and the manner in which they are employed rather than inspecific circuit embodiments. Although various circuits may be employed,for purposes of completing the description of the present invention aspecific embodiment which was actually reduced to practice will bedescribed.

FIG. 3 is a complete schematic diagram of of a typical receiver, such asreceiver 20A assumed to be connected at shielded terminal S01 tomicrophone 16A. The receiver, which in the particular embodiment has anarrow bandwidth of SkHz between 40 and 45 kHz, has an output relay 45.It is activated when the microphone detects a supersonic signal in the40 to 45kHz band. Relay 45 has a pair of normally open contacts 46connected to terminals 417 and 48. Thus when the relay is activatedterminals 47 and 43 are shorted out.

FiG. 4, to which reference is now made, is a partial diagram of thepanel unit 24 showing only the relay 46A, lamp L, and buzzer 40. In thisembodiment terminals 47 and 48 of relay 45 are connected to the panelunit 24, by lines 51 and 52, respectively, the latter being grounded.lower from an appropriate source such as V 60-is supplied to unit 24 onlines 54 and 55, the latter being grounded. Line 54 is connected througha power switch 57 and a reset switch 58 to a terminal 60 to which oneend of lamp L and one end of coil 62 of relay 40A are connected. Theother ends of the lamp and coil are connected to line 51. The relayincludes two sets 64 and 65 of normally open contacts. The movablecontacts of sets 64 and 65 are respectively connected to line 51 and toground, while their stationary contacts are interconnected.

In operation as long as line 51 is ungrounded, the relay 40A isdeactivated. However, when a supersonic signal is received by receiver20A relay 45 is activated. Consequently, line 51 is grounded throughline 52 and both relay 40A and lamp L, are energized. Thus, the lamp isilluminated and the normally open contacts close. The relay 40A remainsON through its contacts even though thereafter relay 45 may becomedeenergized. As long as the relay 40A is ON, lamp L remains illuminated.Since the relay remains ON even after the activating signal from relay45 terminates, and remains ON until reset, the relay may broadly bethought of as a latchable relay which is held ON (until reset) byholding currents passing through its contacts.

As shown, the buzzer 40 is connected at one end to the stationarycontacts which are grounded as long as relay 40A is ON. The other end ofthe buzzer is connected to the ungrounded power line 54 at terminal 60through a buzzer switch 63. Thus when the latter is closed and the relay40A is ON, the buzzer is activated. By opening reset switch 58 the relay40A is deactivated or turned OFF, thereby deenergizing both the lamp L Aand buzzer 40.

The rest of the receivers (20B-20N) are similarly connected to the unit24, which includes the rest of the relays and lamps which are connectedin a manner identical with that described for lamp L and relay 40A. Inthis particular embodiment, when the reset switch 58 is opened, thebuzzer 40 and any activated relay are deenergized at the same time.Clearly if desired, a separate reset switch may be provided for eachrelay and the buzzer so that any one unit can be deenergized or resetwithout affecting the others.

Attention is now directed to FIG. 5 which is a crosssectional view of atypical transmitter, such as transmitter 32A designed to provide aringing rather than a pulse type supersonic signal. The particulartransmitter is shown consisting of an outer cylindrical easing made upof two sections 71 and 72. Section 71 has a short externally threadedstep 710 and section 72 has a corresponding internally threaded recess72a which are mated when the device is assembled as subsequentlydescribed. Section 71 is provided with a central bore 71b, which acompression spring 73 fits, and an internally threaded recess 7110, inwhich a spring retainer 74 may be adjustably threaded. Reducedprojection 74a of the retainer fits into one end of spring 73. A hammer75 which is slidably retained in bore 71b of section 7T, has a reducedprojection 75a which fits into the other end of spring 73.

Section 71 is also provided with an L-shaped slot 76 which can be seenin plan view in W6. 6. Slot 76 is provided for retaining trigger 77 inposition for cocking hammer 75. On of the useful features of the lateralsection 76a of slot 76 is that when the transmitter is worn in a pocketin the manner of a pen. Should the wearer be grabbed, the cocked hammer75 will be released by the jarring action of any altercation in which hemay be involved. Trigger 77 consists of finger-operable button 77a whichis connected with hammer 75 by means of threaded stud 77b, screwed intothe hammer. Hammer 75 thus can be set in cocked position by firstshifting button 77a axially in slot 76 toward detent portion 76a, and bythen laterally rotating button 77a until stud 77b is engaged in thedetent. Shifting button 77a as described compresses spring 73. Theextent of this compression is determined by the position of retainer 74in portion 71c of section 71.

On release of trigger 77 from the detent, the free end of hammer 75impacts one end of vibrator 78 with great force, setting the latter intovibration at its resonant frequency in the manner of a tuning fork.Vibrator 78 is a metallic rod which is provided near its center with aring groove for retaining a thin, flexible suspension disk 79. Theflange of disk 79 is retained between sections 71 and 72 in groove 72bof the latter when the sections are threaded together in assembly. Thisprovides a relatively free suspension for vibrator 78.

When rod 78 is impulsed by hammer 75, after release of trigger 77, itproduces vibrations which emanate from the open end 80 of section 72.The dimensions of vibrator or rod 78 are chosen so that its resonantfrequency is in the supersonic range, e.g., 45kHz. By suspending the rod78 by disk 79, once imparted by hammer 75 it is free to resonate, orring for a significant period, since except for the disk friction it iseffectively undamped.

The size of the transmitter is quite small, generally like a ballpointpen, so that it can be concealably carried and used by the instructorwithout being noticed by the students. Thus the instructor can summonhelp without the students becoming aware of the request. Herebefore itwas assumed that one microphone is intalled in each instrumented area,such as a classroom or the like. Clearly, if desired, severalmicrophones stratigically located in each area may be used to feed asingle receiver. This is particularly desirable in large areas such asthe school cafeteria or gym to insure that when a transmitter isactivated in such an area, the supersonic signals are detected by atleast one of the microphones.

Herebefore it was also assumed that the output of any receiver is usedto illuminate a lamp associated therewith in the display unit andoptionally further activate a buzzer. In schools equipped with two-waycommunication units between the classrooms and the administrativeoffice, the receiver output may further be used to activate the two-waycommunication unit between the particular classroom and the office. Thiswould enable the teacher requesting assistance to audibly communicatewith the office personnel.

The two-way communication unit between each classroom and the office maybe represented by a microphone-speaker 92 (see H6. 7) installed in theclassroom and connected to a microphone speaker 93 in the school officeby a two-way amplifier 94. The receiver output relay 415 (see FIG. 3)may include an additional set of contacts connected to the amplifier 94.When an emergency arises in the room and the receiver is activated bythe detection of the supersonic signal produced by theinstructor-activated transmitter, these additional contacts may be usedto control the amplifier gain automatically, e.g., increase it andthereby enable the instructor to audibly communicate with the officepersonnel. This feature may be particularly desirable under extremeemergencies which may prevent the instructor from directly activatingthe microphonespeaker 92 in the room.

There has accordingly been shown and described herein a novel emergencyalarm system for schools or the like. The system enables an instructorin any classroom or other instrumented area to indicate to personnel inan administrative office the existence of an emergency in his area andrequest aid without others in the area being aware of the request. Thesystem comtemplates the installation of a microphone and a narrow bandtuned receiver in each instrumented area. When an emergency arises, theinstructor, equipped with a small concealable transmitter, handactivates the latter to produce a ringing supersonic signal which ispicked up by the microphone, causing the receiver to produce anactivating output signal. The latter is supplied to a display unit inthe administrative office wherein a lamp, representing the particularclassroom, is illuminated and if desired, a buzzer is energized to alertpersonnel to the existence of an emergency. By incorporating in thedisplay unit one lamp for each instrumented area, the existence ofemergencies in more than one area can be simultaneously displayed. Ifdesired, the output of the receiver of each instrumented area can beused to activate a two-way communication unit to enable the instructor,in case of an emergency, to audibly communicate with the administrativepersonnel.

It is appreciated that those familiar with the art may makemodifications or substitute equivalents in the arrangements herebeforedescribed without departing from the true spirit of the invention.Therefore, it is intended that the claims be interpreted to cover suchmodifications and equivalents.

What is claimed is:

l. In a stationary structure defining a plurality of discrete stationarylocations and a central stationary location, a method of indicating atsaid central location the existence of an emergency in any of saiddiscrete locations, the method including the steps of:

providing in each of said discrete stationary locations fixedly locateddetection means for detecting a supersonic signal generated therein;

providing in said central location display means,

which are directly connected by means of continuous wires to thedetection means in the various discrete locations, and which include aplurality of indicators, each associated with a different detectionmeans and energized when the detection means with which it is associateddetects a supersonic signal; generating in each discrete stationarylocation at which an emergency exists a supersonic signal which isdetected by the detection means in the discrete location; providingaudio means in at least one of said discrete stationary locations, saidaudio means including a variabe gain audio amplifier; and automaticallyincreasing the gain of said amplifier when the detection means in thestationary location detect a supersonic signal which is generatedtherein. 2. In combination with a stationary structure defining aplurality of discrete stationary chambers each adapted to be occupied bya plurality of individuals and a stationary control location, a systemfor indicating at said control location the existence of an emergency inany of said chambers, the system comprising:

separate detection means installed in each stationary chamber fordetecting a non-audible signal generated therein;

control means located in said control location, di-

rectly coupled to said separate detection means and including a separateenergizable indicator for each separate detection means installed ineach chamber, said control means further including means for energizingeach indicator associated with a detection means which detects anonaudible signal;

signal generating means in each discrete stationary location forgenerating a non-audible signal therein; and

audio means associated with at least one of said stationary chambers,said audio means including a variable gain audio amplifier, and meansfor coupling said amplifier to the detection means in said chamber withthe gain of said amplifier increasing when the detection means detect anon-audible sig-

1. In a stationary structure defining a plurality of discrete stationarylocations and a central stationary location, a method of indicating atsaid central location the existence of an emergency in any of saiddiscrete locations, the method including the steps of: providing in eachof said discrete stationary locations fixedly located detection meansfor detecting a supersonic signal generated therein; providing in saidcentral location display means, which are directly connected by means ofcontinuous wires to the detection means in the various discretelocations, and which include a plurality of indicators, each associatedwith a different detection means and energized when the detection meanswith which it is associated detects a supersonic signal; generating ineach discrete stationary location at which an emergency exists asupersonic signal which is detected by the detection means in thediscrete location; providing audio means in at least one of saiddiscrete stationary locations, said audio means including a variabe gainaudio amplifier; and automatically increasing the gain of said amplifierwhen the detection means in the stationary location detect a supersonicsignal which is generated therein.
 2. In combination with a stationarystructure defining a plurality of discrete stationary chambers eachadapted to be occupied by a plurality of individuals and a stationarycontrol location, a system for indicating at said control location theexistence of an emergency in any of said chambers, the systemcomprising: separate detection means installed in each stationarychamber for detecting a non-audible signal generated therein; controlmeans located in said control location, directly coupled to saidseparate detection means and including a separate energizable indicatorfor each separate detection means installed in each chamber, saidcontrol means further including means for energizing each indicatorassociated with a detection means which detects a non-audible signal;signal generating means in each discrete stationary location forgenerating a non-audible signal therein; and audio means associated withat least one of said stationary chambers, said audio means including avariable gain audio amplifier, and means for coupling said amplifier tothe detection means in said chamber with the gain of said amplifierincreasing when the detection means detect a non-audible signal in saidchamber.